Numerous applications exist at the present time for which it is desirable to obtain a representation of the spatial distribution of charged particles emerging from a surface, such as, for example, the electrons emitted by a radioactive layer formed by a section of a biological analysis preparation.
Various devices have been described up to now, allowing such representations to be obtained. Among these may be mentioned the European Patent Applications EP 0,395,510 and EP 0,376,762, the inventor of which is Mr. Georges CHARPAK, which describe systems based on the phenomenon of luminous avalanche.
Such devices give satisfaction. However, these devices, entailing optical detection of the abovementioned luminous avalanche phenomenon, are more particularly intended for bidimensional imagery for which resolution per surface points of the order of 0.01 mm.sup.2 is necessary.